1. Field of the Invention
The present invention relates to a linear compressor, and more particularly, to a linear compressor in which an inner circumferential surface of an inner stator assembly is attached onto an outer circumferential surface of a cylinder to reduce an inner diameter of a magnet assembly, thereby reducing the amount of magnet used and the size of the equipment.
2. Description of the Background Art
FIG. 1 shows a linear compressor in accordance with a conventional art. As shown in the drawing, a general linear compressor is driven by a linear motor consisting of an inner stator assembly 4A, an outer stator assembly 4B, that is, a stator, and a magnet assembly 5, that is, the rotor.
The linear compressor includes a compression unit C installed in a horizontal direction inside a casing V filled with oil at its bottom, for sucking, compressing and discharging, and a oil feeder O fixedly combined at the outside of the compression unit C, to provide oil to each contact sliding portion (sliding portion) of elements.
The structure of the compression unit C will now be described.
The compression unit C includes a circular frame 1, a cover 2 fixed at a rear side (in the description to be made hereinafter, the compression stroke direction of the piston is expressed as a front side, and its opposite direction is expressed as a rear side) of the frame 1; a cylinder 3 fixedly installed in the horizontal direction at the center of inside of the frame 1; an inner stator assembly 4A fixed at the frame 1 with a predetermined space xe2x80x98pxe2x80x99 from the outer circumferential surface of the cylinder 3; an outer stator assembly 4B fixedly installed at the frame 1 with a predetermined gap at the outer circumferential surface of the inner stator assembly 4A to form an induced magnetic flux along with the inner stator assembly 4A; a magnet assembly 5 inserted in the gap between the inner/outer stator assemblies 4A and 4B to make a linear reciprocal movement; a piston 6 incorporated to the magnet assembly 5 and sucking and compressing a coolant gas while being slidably moved inside the cylinder; an inner resonance spring 7A and an outer resonance spring 7B for inducing the magnet assembly 5 to continuously make a resonance movement in the gap between the inner/outer stator assemblies 4A and 4B.
The inner resonance spring 7A and the outer resonance spring 7B are all compressive coil springs. The inner resonance spring 7A is inserted between the outer circumferential surface of the cylinder and the inner circumferential surface of the inner stator assembly 4A so as to be extrapolated in the cylinder 3 at predetermined gaps, of which the front side end portion is supported by one end portion of the frame 1 and its rear side end portion is supported by the inner surface of the magnet assembly 5.
As shown in FIG. 2, the inner diameter D2 of the outer resonance spring 7B is formed to be the same as the inner diameter D1 of the inner resonance spring 7A, positioned to form a concentricity with the inner resonance spring 7A.
The front side end portion of the outer resonance spring 7B is supported by the outer surface of the magnet assembly 5 where the rear side end portion of the inner resonance spring 7A is supported, and its rear side end portion is supported by the inner surface of the cover 2 of the compression unit C.
Reference numeral 8 denotes a suction valve, 9 denotes a discharge valve assembly, d1 denotes the inner diameter of the inner stator assembly, d2 denotes the inner diameter of the magnet assembly, and S denotes a compression space.
The operation of the linear compressor of the conventional art constructed as described above will now be explained.
When a current is applied to the stator of the linear motor consisting of the inner stator assembly 4A and the outer stator assembly 4B and thus an induced magnetic flux is generated, the magnet assembly 5, that is, the rotor, inserted between the stators makes a linear reciprocal movement, according to which the piston 6 combined to the magnet assembly 5 moves reciprocally within the cylinder 3.
As the piston 6 moves reciprocally within the cylinder 3, the coolant gas flowing into the casing V is compressed in the cylinder 3 and then discharged by pushing the discharge valve assembly 8.
At this time, the inner resonance spring 7A elastically supporting the inside of the magnet assembly 5 inserted between the cylinder 3 and the inner stator assembly 4A and the outer resonance spring 7B elastically supporting the outside of the magnet assembly 5 store the liner reciprocal movement of the magnet assembly 5 to which the piston 6 is integrally combined as an elastic energy, induces a resonance movement of the magnet assembly 5 by converting the stored elastic energy to a linear movement.
However, as to the conventional linear compressor, since the inner resonance spring is inserted between the outer circumferential surface of the cylinder and the inner circumferential surface of the inner stator assembly, the inner diameter of the inner stator assembly is greater than that of the inner resonance spring. Accordingly, the inner diameter of a magnet holder of the magnet assembly inserted between the outer circumferential surface of the inner stator assembly and the inner circumferential surface of the outer stator assembly is enlarged. This causes the high-priced magnet needed for construction of the magnet assembly and required for the output of the motor to be enlarged, causing the size of the motor to be increased, as well as the production cost.
Therefore, an object of the present invention is to provide a linear compressor in which the amount of a magnet to be used is reduced by minimizing the size of the inner diameter of an inner stator assembly, thereby reducing a production cost of the compressor.
Another object of the present invention is to provide a linear compressor in which a plurality of the inner resonance springs or a plurality of outer resonance springs are provided, so that a reliability of the resonance movement of a magnet assembly is improved.
To achieve these and other advantages and in accordance with the purposed of the present invention, as embodied and broadly described herein, there is provided a linear compressor including: a cover fixed at a rear side of a frame; a cylinder fixedly installed in a horizontal direction at the center of inside of the frame; an inner stator assembly fixedly installed at the frame in a state that its inner circumferential surface contacts an outer circumferential surface of the cylinder; an outer stator assembly fixedly installed at the frame, being spaced apart from the inner stator assembly to the outer periphery for a predetermined distance; a magnet assembly incorporated with a piston, making a linear reciprocal movement with one end portion thereof inserted in the gap between the inner stator assembly and the outer stator assembly; at least one inner resonance spring supported by the magnet assembly; and a plurality of outer resonance springs supported between the magnet assembly and the cover.